System and method for multiplexing control and data channels in a multiple input, multiple output communications system

ABSTRACT

A system and method for system and method for multiplexing control and data channels in a multiple input, multiple output (MIMO) communications system are provided. A method for transmitting control symbols and data symbols on multiple MIMO layers includes selecting a first set of codewords from N cw  codewords, distributing control symbols onto the first set of layers, placing data symbols of the first set of codewords onto the first set of layers, placing data symbols of the (N cw -N cw1 ) remaining codewords to remaining layers if N cw &gt;N cw1 , and transmitting the multiple MIMO layers. The first set of codewords is associated with a first set of layers from the multiple MIMO layers, and the N cw  codewords are to be transmitted simultaneously and the first set of codewords comprises N cw1  MIMO codewords, where N cw  and N cw1  are integers greater than or equal to 1. The remaining layers are MIMO layers from the multiple MIMO layers not in the first set of layers.

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/293,985, filed on Jan. 11, 2010, and entitled“System and Method for Multiplexing Control and Data Channels in aMultiple Input, Multiple Output Communications System,” whichapplication is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates generally to wireless communications, andmore particularly to a system and method for multiplexing control anddata channels in a multiple input, multiple output (MIMO) communicationssystem.

BACKGROUND

For 3GPP Rel-8 (commonly referred to as Long Term Evolution (LTE)),broadly speaking, uplink control information may be sent in two ways:(a) without simultaneous transmission of data (i.e., uplink sharedchannel (UL-SCH)); and (b) with simultaneous transmission of UL-SCH.Here we are concerned with (b) where control and data are sent on thesame subframe.

When user equipment (UE) has a valid scheduling grant, network resourcesare assigned for the UL-SCH in a corresponding subframe. In thesubframe, the uplink layer 1 (L1)/layer 2 (L2) control signaling may bemultiplexed with the coded UL-SCH onto a physical uplink shared channel(PUSCH) prior to modulation and discrete Fourier transform (DFT)transform precoding. The control signaling may include hybrid automaticrepeat request (HARQ) acknowledgements and channel status reports.

SUMMARY OF THE INVENTION

These and other problems are generally solved or circumvented, andtechnical advantages are generally achieved, by embodiments of a systemand method for multiplexing control and data channels in a multipleinput, multiple output (MIMO) communications system.

In accordance with an embodiment, a method for transmitting controlsymbols and data symbols on multiple input, multiple output (MIMO)layers is provided. The method includes selecting a first set ofcodewords from N_(cw) codewords, distributing control symbols onto thefirst set of layers, placing data symbols of the first set of codewordsonto the first set of layers, placing data symbols of the(N_(cw)-N_(cw1)) remaining codewords to remaining layers ifN_(cw)>N_(cw1), and transmitting the multiple MIMO layers. The first setof codewords is associated with a first set of layers from the multipleMIMO layers, and the N_(cw) codewords are to be transmittedsimultaneously and the first set of codewords comprises N_(cw1) MIMOcodewords, where N_(cw) and N_(cw1) are integers greater than or equalto 1. The remaining layers are MIMO layers from the multiple MIMO layersnot in the first set of layers.

In accordance with an embodiment, a method for transmitting controlsymbols and data symbols on multiple input, multiple output (MIMO)layers is provided. The method includes constructing one or morecodewords to be simultaneously transmitted over a plurality of MIMOlayers, distributing control symbols over the plurality of MIMO layers,placing data symbols of the one or more codewords onto the plurality ofMIMO layers, and transmitting the multiple MIMO layers.

In accordance with an embodiment, a method for transmitting controlsymbols and data symbols on multiple input, multiple output (MIMO)layers is provided. The method includes selecting a codeword from aplurality of codewords, distributing control symbols onto the subset ofMIMO layers, placing data symbols of the plurality of codewords onto theplurality of layers, and transmitting the multiple MIMO layers. Theplurality of codewords are to be transmitted over a plurality of MIMOlayers, and the selected codeword is to be transmitted over a subset ofMIMO layers of the plurality of MIMO layers.

An advantage of an embodiment is that control signals multiplexed ontomultiple MIMO layers may help with diversity processing gain.

Yet another advantage of an embodiment is that multiplexing the controlsignals onto multiple MIMO layers based on the type, requirements, andnature of the control information is transmitted. For example, CQI/PMIcontrol signals may be mapped onto different MIMO layers or CWs ornumber of MIMO layers than HARQ ACK/NACK or RI.

The foregoing has outlined rather broadly the features and technicaladvantages of the present invention in order that the detaileddescription of the embodiments that follow may be better understood.Additional features and advantages of the embodiments will be describedhereinafter which form the subject of the claims of the invention. Itshould be appreciated by those skilled in the art that the conceptionand specific embodiments disclosed may be readily utilized as a basisfor modifying or designing other structures or processes for carryingout the same purposes of the present invention. It should also berealized by those skilled in the art that such equivalent constructionsdo not depart from the spirit and scope of the invention as set forth inthe appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the embodiments, and the advantagesthereof, reference is now made to the following descriptions taken inconjunction with the accompanying drawings, in which:

FIG. 1 is a space diagram of a multiplexing of control and data in LTE;

FIG. 2 is a diagram of a transmitter structure of rank-2 UL transmissionusing two TBs for two transmit antennas in the case of no ACK/NACKspatial bundling without layer shifting;

FIG. 3 is a diagram of a transmitter structure of rank-2 UL transmissionusing two TBs for two transmit antennas in the case of ACK/NACK spatialbundling with layer shifting;

FIG. 4 a is a diagram of a single codeword to a single layer mapping inLTE;

FIG. 4 b is a diagram of a mapping of two codewords to two layers;

FIG. 4 c is a diagram of a mapping of two codewords to three layers;

FIG. 4 d is a diagram of a mapping of two codewords to four layers;

FIG. 4 e is a diagram of a mapping of one codeword to two layers;

FIG. 5 is a space diagram of two MIMO layers containing control and datafrom a single codeword;

FIG. 6 is a space diagram of two MIMO layers containing control and datafrom two codewords;

FIG. 7 is a space diagram of three MIMO layers containing control anddata from two codewords; and

FIG. 8 is a space diagram of two MIMO layers containing control and datafrom two codewords.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of the embodiments are discussed in detail below.It should be appreciated, however, that the present invention providesmany applicable inventive concepts that can be embodied in a widevariety of specific contexts. The specific embodiments discussed aremerely illustrative of specific ways to make and use the invention, anddo not limit the scope of the invention.

FIG. 1 illustrates space diagram 100 of a multiplexing of control anddata in LTE. As shown in FIG. 1, control and data are multiplexed onto asingle uplink layer. Space diagram 100 may be partitioned into differentzones with the zones carrying different information. Zones hashed with asimilar hashing pattern carry similar information. For example, zone 105may be used to carry a reference signal, e.g., a pilot. While zone 110may be used to carry UL-SCH data, zone 115 may be used to carry channelquality indicator and/or precode matrix indication information, zone 120may be used to carry ACKs/NACKs used in HARQ, and zone 125 may be usedto carry rank indicator information.

Each zone may contain a plurality of resource elements (REs) with anexact number of resource elements assigned to an individual zone beingdependent on factors such as coding and modulation scheme being used,communications system configuration, number of UE operating, and soforth. The proportions of the various zones shown in space diagram 100are not intended to illustrate precise relationships of the amount ofresource elements allocated to the various zones, but to convey arelative relationship and arrangement of the zones.

For 3GPP Rel-10 (commonly referred to as LTE-Advanced (LTE-A)), atransmission block (TB) may be mapped to a MIMO codeword (CW) after achain of processing including channel coding, rate matching, modulation,and so on, the same as in LTE. However, the maximum number of MIMOlayers in LTE-A uplink is increased to four and the maximum number ofMIMO codewords is increased to two.

In contrast to downlink MIMO, uplink (UL) MIMO of LTE-A is consideringadopting layer shifting together with ACK/NACK spatial bundling in theprocessing chain. FIG. 2 illustrates a transmitter structure 200 ofrank-2 UL transmission using two TBs for two transmit antennas in thecase of no ACK/NACK spatial bundling without layer shifting. FIG. 3illustrates a transmitter structure 300 of rank-2 UL transmission usingtwo TBs for two transmit antennas in the case of ACK/NACK spatialbundling with layer shifting.

FIG. 4 a illustrates a single codeword to a single layer mapping in LTE.FIG. 4 b illustrates a mapping of two codewords to two layers. FIG. 4 cillustrates a mapping of two codewords to three layers. FIG. 4 dillustrates a mapping of two codewords to four layers. FIG. 4 eillustrates a mapping of one codeword to two layers. If the design usedin DL LTE is used, then the mapping shown in FIG. 4 e may only be usedfor retransmissions where an initial transmission used two layers tosend the TB. Further, the combinations of codeword (CW) to layer mappingshown in FIG. 4 a through FIG. 4 e can be used for LTE-Advanced uplink.

As stated in TR36.814, “simultaneous transmission of uplink L1/L2control signaling and data is supported through two mechanisms:

-   -   Control signaling is multiplexed with data on PUSCH according to        the same principle as in Rel-8    -   Control signaling is transmitted on physical uplink control        channel (PUCCH) simultaneously with data on PUSCH.”

Although control may be transmitted on PUCCH simultaneously with data onPUSCH, control signaling multiplexing with data on PUSCH is still neededfor at least the following cases:

-   -   Multiplexing data and control on PUSCH reduces CM and hence        increases the coverage.    -   When CQI/PMI/RI and maybe other channel state information is        triggered by PDCCH that assigns UL-SCH transmission, such        control information has to be multiplexed together with data on        PUSCH.

When only one MIMO layer is being used, the same control-datamultiplexing scheme as described for 3GPP Release-8 should be used(shown in FIG. 1). New designs of control-data multiplexing arediscussed below for cases with multiple MIMO layers, e.g., one or morecodewords mapped to two, three, or four MIMO layers (shown in FIGS. 4 bthrough 4 e).

The multiplexing of control-data to multiple MIMO layer PUSCHtransmission may take several approaches: single codeword or allcodewords.

Single codeword rule—Select layers associated with one of the codewordsfor control-data multiplexing. A criteria or rule may be needed toselect an appropriate codeword. The codeword may be selected explicitly(for example, select a first codeword) via higher layer signaling ordynamic physical downlink control channel (PDCCH) signaling.Alternatively, the codeword may be selected implicitly using a) acodeword's modulation and coding scheme (MCS) level as provided in thePDCCH that assigns the PUSCH, b) a codeword's signal plus interferenceto noise ratio (SINR), c) a number of layers occupied by a codeword, d)an impact of a codeword on PUSCH performance, e) HARQ transmissionstatus, for example, initial versus re-transmissions or a combinationthereof.

All codewords rule—Use all the MIMO layers for control-datamultiplexing. When one codeword is mapped to two layers, the singlecodeword strategy degenerates to the all codewords strategy.

The performance comparison and selection for a final solution dependsheavily on whether ACK/NACK spatial bundling (LS/ANB) with layershifting is used for UL MIMO transmissions. Further considerations mayinclude the type of receiver (successive interference cancellation (SIC)versus minimum mean-square error (MMSE)) that an enhanced NodeB (eNB) islikely to implement, whether re-transmission is on one of the codewordsin case of no LS/ANB, size (number of bits) of the control information(relative to that of the PUSCH resource allocated). In addition,different consideration may be needed for CQI/PMI versus ACK/NACK and RIfor diversity and coverage purposes. For example, CQI/PMI may be mappedto different layers or CWs, or a different number of layers or CWs, thanthe ACK/NACK or RI.

Although LTE control information, such as ACK/NACK, RI, CQI/PMI, isdiscussed herein, other control signaling, such as carrier indicators,may be processed in a similar manner in LTE-A.

Control Information on a Single Codeword.

Since control information is important for the proper functioning of acommunications system, they need to be protected as much as possible tothat they may be received by the eNB correctly. Furthermore, the controlinformation is relatively small and is protected by relatively weakcodes, such as block codes and convolutional codes, thus a physicalchannel with better quality should be used to carry the controlinformation.

Therefore, if there are multiple MIMO layers, design considerations mayinclude:

-   -   The control information should be mapped to layers with better        quality. For example, for two codewords mapped to two layers,        assuming that layer two is better than layer one, then the        control information should be mapped to layer two, leaving layer        one completely for data only.    -   It may be simpler for the receiver if the control information is        mapped to layers belonging to a same codeword.    -   If the control information is to be multiplexed with a codeword        X, the control information should be mapped to all layers of        codeword X. Doing so allows the control information to take        advantage of diversity between layers.    -   If the control information is mapped to multiple layers, it        should occupy the same resource elements across the multiple        layers.

Thus for the codeword-to-layer mapping scenarios shown in FIGS. 4 athrough 4 e, the control-data multiplexing is as follows. In the figuresto be discussed below, the illustrated locations of the control signals,e.g., FIGS. 1, 5-8, the amount of resource elements allocated for eachtype of control signaling is for illustration only. As in LTE, thenumber of modulation symbols for each type of control signaling will becalculated as a function of several variables. Then a rule may be usedto assign the modulation symbols to the resource elements till all themodulation symbols are exhausted. The number of modulation symbolsallocated in each layer/slot may vary.

One codeword mapped to one layer: Reuse 3GPP Release-8 design (FIG. 1).

One codeword mapped to two layers: FIG. 5 illustrates a space diagram500 of two MIMO layers containing control and data from a singlecodeword. Control information (contained in zone 505 and zone 506 aswell as zones 510-513) may be multiplexed onto both layers, whereincontrol modulation symbols occupy the same (or approximately the same)resource elements in both layers. As illustrated in FIG. 5, theinformation carried over zones, such as zones 510-513, may betime-division multiplexed with the data. As specified in LTE Rel-8,zones 510-513 may also be used to carry HARQ ACK/NACK information andrank indicator (RI).

Two codewords mapped to two layers: FIG. 6 illustrates a space diagram600 of two MIMO layers containing control and data from two codewords.Map control information to a layer according to single codeword rule asdiscussed previously (zone 605 and zones 615 and 616). Let the layercarrying the control information be referred to as layer X. Within layerX, the multiplexing of control and data reuses the 3GPP Release-8design. Here the control information includes not only CQI, ACK/NACK, RIused in Release-8, but it also includes any new type of controlinformation that may be defined for Release-10 or later, e.g., indicatorfor carrier aggregation and COMP, etc. Zone 610 carries data fromcodeword with control and data, while zone 611 carries data fromcodeword with only data.

Two codewords mapped to three layers: FIG. 7 illustrates a space diagram700 of three MIMO layers containing control and data from two codewords.As shown in FIG. 7, a first codeword (let it be referred to as CW1) ismapped to one layer and a second codeword (let it be referred to as CW2)is mapped to two layers. Clearly, CW2 contains twice as many modulationsymbols as CW1 if control information is excluded. Thus, if controlinformation is punctured into the data modulation symbols, multiplexingcontrol symbols with CW2 may be better than multiplexing with CW1 interms of a number of data modulation symbols being punctured from acodeword. Zone 705 and zones 720 and 721 contain control informationfrom codeword containing control and data, zone 710 contains data fromcodeword containing control and data, and zone 715 contains data fromcodeword containing only data.

Two codewords mapped to four layers: Each codeword is mapped to two MIMOlayers. Let a first codeword where control information resides bedenoted codeword X. Codeword X is selected according to single codewordrule as discussed previously. Within codeword X, multiplexing of controland data may be performed as with codeword CW2 in the case with twocodewords mapped to three layers.

Control Information on all Codewords.

In the situation where control information is contained in allcodewords, then the control information may be always mapped to all MIMOlayers. As discussed herein, all codewords means that there are two ormore codewords. Therefore, situations where one codeword is mapped toone or two layers may not be considered. FIG. 8 illustrates a spacediagram 800 of two MIMO layers containing control and data from twocodewords. As shown in FIG. 8, control information may be mapped to bothlayers, while data from each of the two codewords are mapped to a singlelayer. The mapping of control and data from two codewords to two MIMOlayers as shown in FIG. 8 may have an advantage of maximizing spatialdiversity for the control information as well as better coverage ofcontrol information. Zones 805 and 806 as well as zones 815 through 818carry control information from both codewords, while zone 810 carriesdata from a first codeword and zone 811 carries data from a secondcodeword.

However, resource assignment of control signaling may be difficult dueto separate processing of two transmission blocks. For example, twotransmission blocks may have different modulation orders, therebycausing control information to use two different modulation orders. If aSIC receiver is used, mapping control information to all layers may makeit difficult to implement the cancellation. Additionally, if ACK/NACKspatial bundling with layer shifting is adopted, full or close to fullspatial diversity may be available to each layer, making all codewordmapping even more unattractive.

In 3GPP Release-8, formulas for determining a number of coded symbolsfor HARQ-ACK or rank indicator and channel quality information are:

$Q^{\prime} = {\min\begin{pmatrix}{\left\lceil \frac{O \cdot M_{sc}^{{PUSCH} - {initial}} \cdot N_{symb}^{{PUSCH} - {initial}} \cdot \beta_{offset}^{PUSCH}}{\sum\limits_{r = 0}^{C - 1}\; K_{r}} \right\rceil,} \\{4 \cdot M_{sc}^{PUSCH}}\end{pmatrix}}$ and $Q^{\prime} = {{\min\begin{pmatrix}{\left\lceil \frac{\left( {O + L} \right) \cdot M_{sc}^{{PUSCH} - {initial}} \cdot N_{symb}^{{PUSCH} - {initial}} \cdot \beta_{offset}^{PUSCH}}{\sum\limits_{r = 0}^{C - 1}\; K_{r}} \right\rceil,} \\{{M_{sc}^{PUSCH} \cdot N_{symb}^{PUSCH}} - \frac{Q_{RI}}{Q_{m}}}\end{pmatrix}}.}$

To extend to multiple layer PUSCH transmissions, the formulas need to beupdated as well. Note that while ACK/NACK, RI, and CQI are used asexamples of control information, similar formula may be used to carryother types of control information, e.g., the indicator for carrieraggregation and COMP, etc. The formulas are not to be interpreted to belimited to any specific control information type. Formulas for thesingle codeword case are shown below.

-   -   ACK/NACK (RI) for single codeword:

${Q^{\prime} = {\min\begin{pmatrix}{\left\lceil \frac{O \cdot M_{sc}^{{PUSCH} - {initial}} \cdot N_{symb}^{{PUSCH} - {initial}} \cdot N_{layer} \cdot \beta_{offset}^{PUSCH}}{\sum\limits_{r = 0}^{C - 1}\; K_{r}} \right\rceil,} \\{4 \cdot M_{sc}^{PUSCH} \cdot N_{layer}}\end{pmatrix}}},$where N_(layer) is the number of layers for the multiplexing CW. Inaddition, the order of mapping REs across layers need to be defined.

-   -   CQI for single codeword:

$Q^{\prime} = {{\min\begin{pmatrix}{\left\lceil \frac{\left( {O + L} \right) \cdot M_{sc}^{{PUSCH} - {initial}} \cdot N_{symb}^{{PUSCH} - {initial}} \cdot N_{layer} \cdot \beta_{offset}^{PUSCH}}{\sum\limits_{r = 0}^{C - 1}\; K_{r}} \right\rceil,} \\{{M_{sc}^{PUSCH} \cdot N_{symb}^{PUSCH} \cdot N_{layer}} - \frac{Q_{RI}}{Q_{m}}}\end{pmatrix}}.}$In addition, an order of mapping resource elements across layers need tobe defined.Formulas for the all codeword case are shown below.

-   -   ACK/NACK for all codewords:

$\begin{matrix}{Q^{\prime} = {\min\begin{pmatrix}{\left\lceil \frac{O \cdot \left( {N_{{layer},1} + N_{{layer},2}} \right)}{{N_{{layer},1} \cdot \frac{{MPR}_{1}}{\beta_{1}}} + {N_{{layer},2} \cdot \frac{{MPR}_{2}}{\beta_{2}}}} \right\rceil,} \\{4 \cdot M_{sc}^{PUSCH} \cdot \left( {N_{{layer},1} + N_{{layer},2}} \right)}\end{pmatrix}}} \\{= {\min\begin{pmatrix}{\left\lceil \frac{O \cdot M_{sc}^{{PUSCH} - {initial}} \cdot N_{symb}^{{PUSCH} - {initial}} \cdot \left( {N_{{layer},1} + N_{{layer},2}} \right)}{\frac{\sum\limits_{r = 0}^{C_{1} - 1}\; K_{r,1}}{\beta_{1}} + \frac{\sum\limits_{r = 0}^{C_{2} - 1}\; K_{r,2}}{\beta_{2}}} \right\rceil,} \\{4 \cdot M_{sc}^{PUSCH} \cdot \left( {N_{{layer},1} + N_{{layer},2}} \right)}\end{pmatrix}}} \\{= {\min\begin{pmatrix}{\left\lceil \frac{O \cdot M_{sc}^{{PUSCH} - {initial}} \cdot N_{symb}^{{PUSCH} - {initial}} \cdot \left( {N_{{layer},1} + N_{{layer},2}} \right) \cdot \beta_{offset}^{PUSCH}}{{\sum\limits_{r = 0}^{C_{1} - 1}\; K_{r,1}} + {\sum\limits_{r = 0}^{C_{2} - 1}\; K_{r,2}}} \right\rceil,} \\{4 \cdot M_{sc}^{PUSCH} \cdot \left( {N_{{layer},1} + N_{{layer},2}} \right)}\end{pmatrix}}}\end{matrix}$The last step shown above assumes that the two codewords use the sameoffset value (β). MPR_(n) (n=1, 2) is the spectral efficiency associatedto the MCS level of codeword n. To derive this formula, a weighted (bynumber of layers of each codeword) average MPR may be used to calculatethe number coded symbols for the control information while the originalformula of LTE Release-8 uses the MPR of a single codeword. In addition,an order of mapping resource elements across layers and codewords needto be defined. In order to achieve diversity gain, the mapping may befirst made across codewords/layers. In the case that differentmodulation levels are used in the two codewords, coding scheme ofACK/NACK and RI need to be modified.

-   -   CQI for all codewords:

$Q^{\prime} = {\min\begin{pmatrix}{\left\lceil \frac{\begin{matrix}{\left( {O + L} \right) \cdot M_{sc}^{{PUSCH} - {initial}} \cdot N_{symb}^{{PUSCH} - {initial}} \cdot} \\{\left( {N_{{layer},1} + N_{{layer},2}} \right) \cdot \beta_{offset}^{PUSCH}}\end{matrix}}{{\sum\limits_{r = 0}^{C_{1} - 1}\; K_{r,1}} + {\sum\limits_{r = 0}^{C_{2} - 1}\; K_{r,2}}} \right\rceil,} \\{{M_{sc}^{PUSCH} \cdot N_{symb}^{PUSCH} \cdot \left( {N_{{layer},1} + N_{{layer},2}} \right)} - Q_{RI}^{\prime}}\end{pmatrix}}$In addition, the order of mapping resource elements across layers andcodewords need to be defined. In order to achieve diversity gain, themapping may be first made across codewords/layers. In the case thatdifferent modulation levels are used in the two codewords, performanceneed to be verified.Furthermore, rank dependent offset values may be considered for allcases where different values of the offset β may be configured fordifferent number of layers of PUSCH transmission.

Comparison of Options.

In Table 1, the pros and cons of single codeword and all codewordmapping options are compared considering a variety of combinations. Thecomparison shows that single codeword options may be a simpler solutionthan the all codeword options.

TABLE 1 Comparison of Single-CW strategy with All-CW strategy underassumption of (a) layer shifting vs no layer shifting and (b) MMSEreceiver vs SIC receiver. LS with ANB No LS and ANB MMSE Single- Due toANB, balancing the FER Need to select a CW for receiver CW performanceof the 2 CWs need to be multiplexing. considered. All- Same/similar MCSlevel is likely for Different MCS levels are likely CWs both CWs. Due toANB, balancing the for the 2 CWs which make it FER performance of the 2CWs should difficult to determine the number be easy for this setting.of coded symbols for the control information. SIC Single- Selecting CWfor multiplexing could be Selecting CW for multiplexing receiver CWtricky. Due to ANB, balancing the FER could be tricky. performance ofthe 2 CWs need to be considered. All- Different MCS levels may be usedfor Different MCS levels are likely CWs the 2 CWs which make itdifficult to for the 2 CWs which make it determine the number of codedsymbols difficult to determine the number for the control information.In addition, of coded symbols for the control multiplexing control inboth CWs may information. In addition, interrupt the SIC receiverbehavior. Due multiplexing control in both to ANB, balancing the FERperformance CWs may interrupt the SIC of the 2 CWs need to beconsidered. receiver behavior.

Advantageous features of embodiments of the invention may include: amethod for transmitting control symbols and data symbols on multipleMIMO layers, the method comprising: selecting a first set of codewordsassociated with a first set of layers from the multiple MIMO layers fromN_(cw) codewords, wherein the N_(cw) codewords are to be transmittedsimultaneously and the first set of codewords comprises N_(cw1) MIMOcodewords, where N_(cw1) is an integer greater than or equal to 1;distributing control symbols onto the first set of layers; placing datasymbols of the first set of codewords onto the first set of layers;placing data symbols of the (N_(cw)-N_(cw1)) remaining codewords toremaining layers if N_(cw)>N_(cw1); and transmitting the multiple MIMOlayers. The method could further include, wherein the first set ofcodewords comprises a single codeword. The method could further include,wherein the first set of codewords is selected by a communicationsdevice. The method could further include, wherein the first set ofcodewords is selected based on channel quality. The method could furtherinclude, wherein the first set of codewords is selected based on amodulating and coding scheme (MCS) level associated with the codewords.The method could further include, wherein the first set of codewords isselected based on the number of layers associated with the codewords.The method could further include, wherein the first set of codewords isselected based on a level of impact the control symbols have on theperformance of the data transmission of each codeword. The method couldfurther include, wherein the impact is a proportion of control symbolsto data symbols for each codeword. The method could further include,wherein the first set of codewords is selected based on a hybridautomatic repeat request (HARQ) transmission status associated with thecodewords. The method could further include, wherein the first set ofcodewords is selected by a controller serving a communications device.The method could further include, wherein the first set of codewords issignaled to the communications device via a downlink message. The methodcould further include, wherein the first set of codewords comprisesN_(cw) codewords. The method could further include, wherein distributingcontrol symbols onto the first set of layers is based on the MCS levelsof the first set of codewords. The method could further include, whereindistributing control symbols onto the first set of layers is based on aweighted MCS levels of the first set of codewords. The method couldfurther include, wherein distributing control symbols onto the first setof layers comprises distributing control symbols substantially equallyonto the first set of layers. The method could further include, whereinselecting a first set of codewords comprises selecting two differentfirst set of codewords for two different types of control symbols.

Although the embodiments and their advantages have been described indetail, it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of the invention as defined by the appended claims. Moreover, thescope of the present application is not intended to be limited to theparticular embodiments of the process, machine, manufacture, compositionof matter, means, methods and steps described in the specification. Asone of ordinary skill in the art will readily appreciate from thedisclosure of the present invention, processes, machines, manufacture,compositions of matter, means, methods, or steps, presently existing orlater to be developed, that perform substantially the same function orachieve substantially the same result as the corresponding embodimentsdescribed herein may be utilized according to the present invention.Accordingly, the appended claims are intended to include within theirscope such processes, machines, manufacture, compositions of matter,means, methods, or steps.

What is claimed is:
 1. A method for transmitting control symbols anddata symbols on multiple input, multiple output (MIMO) layers, themethod comprising: selecting a first set of codewords from N_(cw)codewords, wherein the first set of codewords is associated with a firstset of layers from the multiple MIMO layers, and wherein the N_(cw)codewords are to be transmitted simultaneously and the first set ofcodewords comprises N_(cw1) MIMO codewords, where N_(cw) and N_(cw1) areintegers greater than or equal to 1; distributing control symbols ontothe first set of layers, wherein a quantity of the control symbols foreach of the first set of layers is determined in accordance with avariable transmission rank-dependent offset of the first set ofcodewords, wherein the offset is different for different transmissionranks each having a different total number of the MIMO layers; placingdata symbols of the first set of codewords onto the first set of layers;placing data symbols of the (N_(cw)-N_(cw1)) remaining codewords toremaining layers if N_(cw)>N_(cw1), wherein the remaining layers areMIMO layers from the multiple MIMO layers not in the first set oflayers; and transmitting the multiple MIMO layers.
 2. The method ofclaim 1, wherein the transmitting the multiple MIMO layers comprisesprecoding the data symbols and the control symbols with a discreteFourier transform (DFT) transform.
 3. The method of claim 1, wherein thefirst set of codewords comprises a single codeword.
 4. The method ofclaim 3, wherein the control symbols comprise channel qualityinformation (CQI), precoding matrix indicators (PMI), or a combinationthereof.
 5. The method of claim 3, wherein the first set of codewords isselected by a controller serving a communications device.
 6. The methodof claim 5, wherein the first set of codewords is signaled to thecommunications device via a downlink message.
 7. The method of claim 5,wherein the first set of codewords is selected based on channel quality.8. The method of claim 5, wherein the first set of codewords is selectedbased on a modulating and coding scheme (MCS) level associated with thecodewords.
 9. The method of claim 5, wherein the first set of codewordsis selected based on the number of layers associated with the codewords.10. The method of claim 5, wherein the first set of codewords isselected based on a level of impact the control symbols have on aperformance of a data transmission of each codeword.
 11. The method ofclaim 10, wherein the level of impact is a proportion of control symbolsto data symbols for each codeword.
 12. The method of claim 5, whereinthe first set of codewords is selected based on a hybrid automaticrepeat request (HARQ) transmission status associated with the codewords.13. The method of claim 1, wherein the first set of codewords comprisesN_(cw) codewords, where N_(cw1)=N_(cw).
 14. The method of claim 13,wherein the control symbols comprise hybrid automatic repeat requested(HARQ) positive acknowledgement (ACK)/negative acknowledgement (NACK)signals, rank indicator (RI) signals, or a combination thereof.
 15. Themethod of claim 13, wherein the control symbols are time divisionmultiplexed with the data symbols such that the control symbols aretime-aligned across the multiple MIMO layers.
 16. The method of claim 1,wherein a size of the control symbols distributed onto the first set oflayers is based on modulating and coding scheme (MCS) levels of thefirst set of codewords.
 17. The method of claim 16, wherein a functionof the MCS levels of the first set of codewords depends on N_(cw1),N_(cw), or a combination thereof.
 18. The method of claim 1, whereindistributing control symbols onto the first set of layers comprisesdistributing control symbols to substantially the same resource elementsacross the first set of layers.
 19. The method of claim 1, whereinselecting a first set of codewords comprises selecting two differentfirst sets of codewords for two different types of control symbols. 20.A method for transmitting control symbols and data symbols on multipleinput, multiple output (MIMO) layers, the method comprising:constructing one or more codewords to be simultaneously transmitted overa plurality of MIMO layers; distributing control symbols over theplurality of MIMO layers, wherein a quantity of the control symbols foreach of the plurality of MIMO layers is determined in accordance with avariable transmission rank-dependent offset of the one or morecodewords, wherein the offset is different for different transmissionranks each having a different total number of the MIMO layers; placingdata symbols of the one or more codewords onto the plurality of MIMOlayers; and transmitting the multiple MIMO layers.
 21. The method ofclaim 20, wherein the control symbols comprise hybrid automatic repeatrequested (HARQ) positive acknowledgement (ACK)/negative acknowledgement(NACK) signals, rank indicator (RI) signals, or a combination thereof.22. The method of claim 20, wherein the control symbols are time-alignedacross each of the plurality of MIMO layers.
 23. The method of claim 20,wherein the control symbols are time-division multiplexed with datasymbols.
 24. A method for transmitting control symbols and data symbolson multiple input, multiple output (MIMO) layers, the method comprising:selecting a codeword from a plurality of codewords, wherein theplurality of codewords are to be transmitted over a plurality of MIMOlayers, and the selected codeword is to be transmitted over a subset ofMIMO layers of the plurality of MIMO layers; distributing controlsymbols onto the subset of MIMO layers, wherein a quantity of thecontrol symbols for each of the subset of MIMO layers is determined inaccordance with a variable transmission rank-dependent offset of theselected codeword, wherein the offset is different for differenttransmission ranks each having a different total number of the MIMOlayers; placing data symbols of the plurality of codewords onto theplurality of layers; and transmitting the multiple MIMO layers.
 25. Themethod of claim 24, wherein the control symbols comprise channel qualityinformation (CQI) and/or precoding matrix indicators (PMI).
 26. Themethod of claim 24, wherein the subset of MIMO layers comprises a singleMIMO layer or two MIMO layers.
 27. The method of claim 24, wherein thesubset of MIMO layers is chosen based on channel quality, access level,or a combination thereof.
 28. A method for transmitting control symbolsand data symbols on multiple input, multiple output (MIMO) layers, themethod comprising: identifying a type of the control symbols; selectinga first set of codewords according to the type of the control symbols;and multiplexing the control symbols with data on the first set ofcodewords, wherein a quantity of the control symbols for each of theMIMO layers is determined in accordance with a variable transmissionrank-dependent offset of the first set of codewords, wherein the offsetis different for different transmission ranks each having a differenttotal number of the MIMO layers.
 29. The method of claim 28, wherein thecontrol symbols comprise hybrid automatic repeat requested (HARQ)positive acknowledgement (ACK)/negative acknowledgement (NACK) signals,rank indicator (RI) signals, or a combination thereof.
 30. The method ofclaim 29, wherein the first set of codewords comprises two or morecodewords.
 31. The method of claim 28, wherein the control symbolscomprise channel quality information (CQI), precoding matrix indicators(PMI), or a combination thereof.
 32. The method of claim 31, wherein thefirst set of codewords comprises a single codeword.
 33. The method ofclaim 32, wherein the first set of codewords is selected based on amodulating and coding scheme (MCS) level associated with the codewords.34. A communications device comprising: a selecting unit configured toselect a first set of codewords from N_(cw) codewords, wherein the firstset of codewords is associated with a first set of layers from aplurality of multiple input, multiple output (MIMO) layers, and whereinthe N_(cw) codewords are to be transmitted simultaneously and the firstset of codewords comprises N_(cw1) MIMO codewords, where N_(cw) andN_(cw1) are integers greater than or equal to 1; a distributing unitcoupled to the selecting unit, the distributing unit configured todistribute control symbols onto the first set of layers, wherein aquantity of the control symbols for each of the first set of layers isdetermined in accordance with a variable transmission rank-dependentoffset of the first set of codewords, wherein the offset is differentfor different transmission ranks each having a different total number ofthe MIMO layers; a placing unit coupled to the distributing unit and tothe selecting unit, the placing unit configured to place data symbols ofthe first set of codewords onto the first set of layers, and to placedata symbols of the (N_(cw)-N_(cw1)) remaining codewords onto remaininglayers if N_(cw)>N_(cw1), wherein the remaining layers are MIMO layersfrom the plurality of MIMO layers not in the first set of layers; and atransmitter coupled to the placing unit, the transmitter configured totransmit the plurality of MIMO layers.
 35. The communications device ofclaim 34, wherein the transmitter is further configured precode the datasymbols and the control symbols with a discrete Fourier transform. 36.The communications device of claim 34, wherein the first set ofcodewords comprises a single codeword, and wherein the control symbolscomprise channel quality information (CQI), precoding matrix indicators(PMI), or a combination thereof.
 37. The communications device of claim36, further comprising a receiver coupled to the selecting unit, thereceiver configured to receive an indicator from a controller servingthe communications device, the indicator comprising information aboutthe first set of codewords.
 38. The communications device of claim 34,wherein the first set of codewords comprises N_(cw) codewords, whereN_(cw1)=N_(cw), and wherein the control symbols comprise hybridautomatic repeat requested (HARQ) positive acknowledgement(ACK)/negative acknowledgement (NACK) signals, rank indicator (RI)signals, or a combination thereof.
 39. The communications device ofclaim 38, wherein the distributing unit is configured to time divisionmultiplex the control symbols with the data symbols so that the controlsymbols are time-aligned across the multiple MIMO layers.
 40. Thecommunications device of claim 34, wherein the distributing unit isconfigured to distribute a size of the control symbols onto the firstset of layers based on modulation and coding scheme (MCS) levels of thefirst set of codewords.
 41. The communications device of claim 34,wherein the distributing unit is configured to distribute the controlsymbols onto the first set of layers so that the control symbols aredistributed to substantially the same resource elements across the firstset of layers.
 42. The communications device of claim 34, wherein theselecting unit is configured to select two different first sets ofcodewords for two different types of control symbols.
 43. Acommunication device comprising: an identifying unit configured toidentify a type of control symbols to be transmitted on a plurality ofmultiple input, multiple output (MIMO) layers; a selecting unit coupledto the identifying unit, the selecting unit configured to select a firstset of codewords according to the type of the control symbols; and amultiplexer coupled to the identifying unit, the multiplexer configuredto multiplex the control symbols with data on the first set ofcodewords, wherein a quantity of the control symbols for each of theMIMO layers is determined in accordance with a variable transmissionrank-dependent offset of the first set of codewords, wherein the offsetis different for different transmission ranks each having a differenttotal number of the MIMO layers.
 44. The communication device of claim43, wherein the selecting unit is configured to select two or morecodewords according to the type of the control symbols, and wherein thecontrol symbols comprise hybrid automatic repeat requested (HARQ)positive acknowledgement (ACK)/negative acknowledgement (NACK) signals,rank indicator (RI) signals, or a combination thereof.
 45. Thecommunication device of claim 43, wherein the selecting unit isconfigured to select a single codeword according to the type of thecontrol symbols, and wherein the control symbols comprise channelquality information (CQI), precoding matrix indicators (PMI), or acombination thereof.
 46. The communication device of claim 45, whereinthe first set of codewords is selected based on a modulating and codingscheme (MCS) level associated with the codewords.